Direction finding system



March 2, 1943. gggum gpg $13,431

DIRECTION FINDING SYSTEM Filed June 27, 1941 .l v I 5% g: F

I ATTOEK {"ll l v Patented Mar. 2, 143

DIRECTION FmDING SYSTEM Kurt Koschmieder, Berlin, Germany; vested in theAlien Property Custodian Application June 27, 1941, Serial No. 400 015In Germany June 2'7, 1940 4 Claims.

In the copending patent application Serial Number 01,129 of K. Holsten,filed July 5, 1941, a direction finding system is described in which anon-directional antenna is fed from a directional antenna and the novelfeature of which is that the field coils of a goniometer or the couplingcoils of a goniometer frame, as the case may be, are each associatedwith a double-wound choke connected in parallel with the respective coiland joined at its center point to the nondirectional antenna.

One of the supply lines from the directional antenna to the goniometermust be grounded. To such end a high frequency cable whose outerconductor is earthed may be arranged to interconnect the directionalantenna and the goniometer, or two parallel lines located in a groundedcable may be used. In this case one of these two lines must be earthed.Such an arrangement requires that a suitable transition means must beprovided between the symmetric antenme, such as a dipole or a frameaerial, and the asymmetric cable. The present invention has for itsobject the provision of a simple and efficient circuit arrangement forconnecting a symmetric antenna to an asymmetric cable, such as aco-axial cable.

According to the present invention, the directional antenna is joined toan asymmetric high frequency line by a transformer constructed asdescribed hereafter by way of example.

In the drawing, Fig. 1 is a circuit diagram showing one embodiment ofthe invention, Fig. 2 is a diagram illustrating a second embodiment.

B, Fig. 1, denotes an antenna of a H- or U- Adcock system. This systemis connected by a cable K to a field coil F of a goniometer. Anysuitable number of such antennae may be arranged in pairs in awell-known manner. The non-directional antenna voltage is derived by adoublewound choke coil D connected as a high impedance path across coilF so that a non-directional antenna, not shown, may be joined to themiddle point A of coil D which provides a low impedance differentialpath for the non-directional antenna. In order to accommodate theasymmetric cable line to the symmetric antenna B the two are coupledtogether by a high frequency transformer T the secondary of which isdivided into halves La, Lb which are wound in opposition to one another.As shown by way of example, the inner conductor of the cable K is joinedto the middle of the secondary coil La,

Lb. The ends of this coil are connected together, as shown at E, and arejoined to the earthed outer conductor of the cable.

Such an arrangement is useful not alone for Adcock antenna systems butalso for stationary frame aerials operating by means of goniometers, andwill also be useful for an arrangement of the kind shown in Fig. 2 byway of example, and which has a dipole Di connected to an amplifyingdevice Q. If the arrangement according to Fig. 2 were constructed withthe aid of the customary coupled coils, one end of the secondary beinggrounded and the other end connected to the grid of an amplifying tube,then the dipole would be loaded unequally because the space capacitiesof the coupled coils entail a countercurrent which is the more intensethe farther the respective end of the secondary coil is remote fromearth.

It will thus be seen that the transformer here described is useful forany arrangement in which a symmetric high frequency line is to becoupled to an asymmetric one.

What is claimed is:

1. In a direction finding system, a directional antenna system, anon-directional antenna system, means for coupling said systemscomprising an asymmetric high frequency line having a grounded and anungrounded conductor, a transformer having a primary winding in circuitwith said directional antenna system and a pair of secondary windings,said secondary windings being wound in opposition to each other, aconnection joining adjacent ends of said windings with the ungroundedconductor of said line, the outer terminals of said windings beingconnected to said grounded conductor, a goniometer field coil connectedin series in said ungrounded conductor, a choke coil connected acrosssaid field coil, said non-directional antenna system being connected tothe middle point of said choke coil.

2. A direction finding system according to claim 1 in which thedirectional antenna system includes a dipole.

3. A direction finding system according to claim 1 in which thedirectional antenna system includes a dipole, with the primary windingof the transformer connected between the poles of said dipole.

4. A system according to claim 1 where the asymmetric high frequencyline is a co-axial cable.

KURT KOSCHMIEDER.

